Spinal Cord – Clinical Anatomy and Physiology (dermatomes, blood supply, shingles, lumbar puncture)



hello in this video we're gonna look at the clinical anatomy of the spinal cord now the spinal cord is part of your central nervous system the spinal cord is a continuation of the brain and the brain stem the spinal cords termination is called conus medullaris which ends at about the l2 vertebral level from this point on you have continuing nerve fibers extending down known as a codec Quanah or the horse's tail the spinal cord is protected and goes through the spinal canal which is basically made up of the vertebrae though the bones the vertebra is dividing two sections you have seven cervical vertebrae you have 12 thoracic 5 lumber you have the sacrum and then you have the coccyx like the vertebrae the spinal cord is also divided into sections you have the cervical thoracic lumbar sacral and coccyx sections each spinal cord section have where segments have nerves coming in and out of it these are known as a spinal nerves the spinal nerves exits from their corresponding vertebral level let's take a look at the cervical spinal cord which is unique because it has eight pairs of spinal nerves the cervical spinal cord is drawn in green here and it's unique because the cervical spinal nerve exits over their corresponding vertebral level so for example the c1 a spinal nerve the cervical one spinal nerve goes over their cervical one vertebral level the tuber body and so on until you have cervical 8 C 8 which exits over the thoracic one vertebra and this is because there is no C 8 vertebra obviously the thoracic spinal cord is here in blue and it has 12 pairs of thoracic spinal nerves the thoracic spinal nerve exits low their corresponding vertebrae t1 exits below the T one vertebra t12 spinal cord exits below the t12 vertebra the lumbar spinal cord here in purple has five pairs of lumbar spinal nerves exiting again below their vertebral sec sections example you have the l1 spinal nerve exiting below the l1 vertebra the sacral spinal cord have five pairs of spinal nerves which exits through the sacral holes finally you have the coccygeal nerve which exits below the coccyx you looking closely at the spinal cord now and the vertebra in more detail we're looking at the thoracic vertebrae as an example the spinal cord goes through the spinal canal of the vertebra the the table discs sits in between the vertebrae the spinal cord have thoracic spinal nerves coming out here represented in blue the spinal cord have the anterior spinal artery and two posterior spinal arteries supplying it let's look at a superior view of the thoracic spinal cord and vertebra now anterior to the vertebral body is the thoracic aorta now the thoracic aorta have posterior artery branches called the posterior intercostal arteries which will supply the ribs the posterior intercostal arteries branch to form the posterior spinal artery and also gives rise to the anterior spinal artery in the thoracic section of the spinal cord let's now focus on the spinal cord in more detail let's take a cross-section of the thoracic spinal cord the spinal cord has absentia butterfly looking structure the dorsal root at the back and the ventral root in the front will form the spinal nerve in this case it would be the thoracic spinal nerve the spinal nerve then a branch and conformed the dorsal ramus and the ventral ramus which essentially will supply and innervate different parts of the body let's now take a cross-section of the cervical spinal cord the butterfly looking structure in the center of the spinal cord is the gray matter of the spinal cord the gray matter is where synapse is between neurons occur here we can find the dendrites and the terminal axons of neurons this is where synapses occur the white matter surrounding the gray matter is where neurons travel through along the spinal cord it therefore contains the neurons axons as we learned the ventral root is found in the anterior aspect of the spinal cord the ventral root of the spinal cord carries motor neurons out from the spinal cord the dorsal root of the spinal cord carries sensory information into the spinal cord and so here we also find the spinal sensory ganglion where the sensory neurons body is located the dorsal and ventral root will form the spinal nerve this in this case is a cervical spinal nerve let's take a look at a cross-section of the lumbar spinal cord now the lumbar spinal cord typically has a large gray matter the dorsal root of the spinal cord carries sensory information for example information from the skin which contains sensory nerve fibers when touch pain is felt these sensory fibers will carry information to a particular spinal cord level the sensory neurons body is at the dorsal root ganglion the sensory neuron will travel to the posterior Horn of the spinal cord the anterior horn of the spinal cord is where the lower motor neurons arise and they will exit the spinal cord through the ventral root and target and infect to organ for example the muscle to complete the section here we have the sacral spinal cord in the coccygeal spinal cord cross-section remember the spinal cord ends at about the l1 l2 vertebral level and this is termed the conus medullaris continuing bundle of fibers from here is a codec wanna next let's talk about dermatomes your skin is innervated by sensory nerve fibers dermatomes our sensory nerve fibers that innervate a segment of skin and is this is associated with a single spinal cord level so for example here's a human body with a dermatome l distribution drawn out this area in green here is innervated by spinal nerve fibers from the cervical spinal cord the dermatome drawn in green here correlates with different sections of the cervical spinal cord this area has sensory nerve fibers which will bring information to the c6 spinal cord level here is c2 c3 c4 c5 c6 c7 and c8 we have eight cervical spinal nerves these segments are the dermatome distribution of the thoracic spinal cord in blue t-1 spinal cord and so on t10 is easy to remember because it is along the umbilical level these segments of skin is innervated by the lumbar nerve sensory fibers for example this area in particular on the knee is innovated by sensory nerve fibers which will bring information to the l4 spinal cord level the skin segment in orange is a Dermatol distribution of the sacral spinal cord levels these include the genitals part of the foot but mainly the posterior aspect of the lower limb here's the back of the left leg as you can see it is innervated by the sacral spinal nerves important to know that s3 s4 s5 dermatome distribution is important in assessing sensation of the anus this area is tested for sensation to see if there's any signs of spinal cord injuries to complete this image let's talk about the face the side of the face here as you can see is innervated by C 2 C 3 C 4 dimensional distribution and the front of the face is not innovated by the cervical spinal nerves well rather there innervated by the trigeminal nerve which is cranial nerve number 5 after learning a bit about dermatomes and sensory nerve fibers we can now discuss some clinical anatomy focusing on the herpes zoster infection also known as shingles shingles is a common infection it's the reactivation of the varicella zoster virus which is the chickenpox virus in the sensory dorsal root or cranial nerve ganglia it manifests in the elderly usually and is characterized by a vesicular rash along a dermatome wall distribution shingles classically has a prodrome phase characterized by pain burns and sharp sensation like itching and tingling as well this is followed by an eruption of a rash usually unilateral vesicular rash which will eventually ulcerate and crushed over in 10 days remember it usually manifests along a specific Dermatol distribution unilateral on one side to understand the pathophysiology briefly let's look at the t7 spinal cord level which innervates the t7 dermatome segments of the skin which is basically the upper abdomen shingles is reactivation of the chickenpox virus what happens is that the chickenpox virus infects a child characterized by a vesicular infect infectious contagious rash all over the face and upper body the can can obviously affect the t-seven dermatome and then it can invade the area and travel along the sensory nerve fiber and essentially rest stay dormant in the dorsal root ganglion years later when the child gets old the chickenpox virus also known as the varicella zoster virus can reactivate may be due to immuno suppression or whatnot but essentially it will become the herpes zoster virus which will travel back up the sensory nerve fiber and express itself along the t7 dermatome wall distribution as shingles here is a photograph of a person who suffers from shingles and you can see that there is a vesicular crusting rash along the trigeminal v1 Dermatol distribution here is another example of persons back and you can see the rash vesicular rash is a is unilateral and it effects the dermatome wall distribution roughly T 1 2 T 3 dermatome distribution the thoracic area let's talk about the blood supply to the spinal cord which we already briefly mentioned the spinal cord receives two main blood supply of the two posterior spinal arteries and the anterior spinal artery these arteries run along the spinal cord the posterior and anterior spinal arteries are branches of different arteries depending on the segment or the section of the spinal cord so for example the upper spinal cord posterior and anterior spinal arteries arise from the vertebral artery a branch of the subclavian artery the spinal arteries also arise from the branch of the subclavian artery called the ascending cervical artery on the thoracic level the thoracic aorta have branches called the posterior intercostal arteries which we talked about that gives rise to the posterior and anterior spinal cord arteries the lower spinal cord arteries are branches of the lumbar artery which is a branch of the abdominal aorta as well as the lateral sacral artery a branch of the internal iliac artery the artery of I hope I pronounce is right Adam cubits is an important artery it is the primary supply to the lower two-thirds of the spinal cord essentially if there's occlusion of the artery of Adam Q it's due to ischemia hypertension or whatever it can cause a person to be paraplegic because again it supplies if the main supply to the lower two-thirds of the spinal cord next let's talk about the meninges the layers that surround the spinal cord and protected meninges comprised of three layers of protective tissue just like you have meninges of the brain this continues to form the meninges of the spinal cord Here I am drawing the spinal cord and I will introduce the meningeal layers one at a time from the very inner one to the outer one and there are three meningeal layers the Pia mater is the inner meningeal layer surrounding the spinal cord the second layer is the arachnoid membrane which extends to the spinal nerve between the pia mater and the arachnoid membrane is the arachnoid space the outermost meningeal layer is the dura mater between the dura mater and the arachnoid membrane is a subdural space above the dura mater is the epidural space now within the arachnoid space the subarachnoid space you can find fluid flowing through it called this cerebral spinal fluid the cerebrospinal fluid also flows through the central canal at the middle of the spinal cord cerebral spinal fluid also known as CSF provides the brain and spinal cord with nutrients CSF is produced in the brain's ventricles let's look at the side view of the spinal cord again and understand the meningeal layers the spinal cord ends at the conus medullaris and the extension of the nerve fibers is the codec huan'er then you have this thing called the filum terminology which is basically connective tissue strand continuing on from the conus medullaris and extend all the way to basically the coccyx the filum terminale a– is divided into the filum terminale internists which is made up of continuation of the pia mater and then you have the filum terminale or externus which is made up of the dura mater and the arachnoid membrane the filum terminale a externus ends at the coccyx this ace after the conus medullaris below l2 is a site where cerebrospinal fluid can be accessed this space is a subarachnoid space a lumbar puncture is a procedure of collecting cerebrospinal fluid from the spinal canal this is a zoomed section of the lumbar region l2 l3 l4 and the l5 vertebra the spinal cord ends again about the l2 vertebral level then you have the continuing cauda equina the horse's tail the pia mater ends and continues as the filum terminale internists inferiorly the codec wonna is within the arachnoid space floating around the whole area is surrounded by the arachnoid membrane and then you have the dura mater after that the arachnoid membrane and dura mater as we know continued down and then envelopes to form the filum terminale externus above the dura mater is the epidural space let us progress out let us now look at the layers after the epidural space first the vertebrae's is supported by many ligaments behind the spinal cord you have the ligamentum flavum inter spinous ligament then you have the supraspinous ligament surrounding the spinous process and the spine supraspinous ligament is the subcutaneous tissue and then you have the skin the goal of a lumbar puncture is to collect cerebrospinal fluid which can be done by sticking a needle through the skin subcutaneous tissue supraspinatus ligament interest spinal ligament ligamentum flavum dura mater and the arachnoid membrane into the subarachnoid space where the CSF thus your spinal fluid is present once the needle is in this space CSF fluid should rip out the needle is typically inserted between the l4 l5 vertebral level to make sure it does not hit the spinal cord a lumbar puncture is both diagnostic and therapeutic therapeutic because it allows intrathecal administration of chemotherapy and antibiotics for example diagnostic in that it can help diagnose meningitis and multiple sclerosis here is an image of a lumbar puncture being performed note the needle in the patient's back most likely it's inserted between the l4 and l5 or l3 and l4 vertebral level and note CSF dripping slowly out of the needle and being collected by a small tube also note the sterile field which is important to prevent the introduction of infection to the spinal cord clinical anatomy obviously the spinal cord can be injured these are classically called spinal cord injuries or lesions or syndromes spinal cord lesions have many causes including penetrating injuries crush injuries gunshot injuries tumors abscess you name it spinal cord lesions can be divided into a few classic types you have complete transection of the spinal cord Hemi section of the spinal cord central spinal cord lesions posterior spinal cord lesions and anterior spinal cord lesions all of which present with differing sensory and motor deficits we won't talk about that in this video but there will be hopefully other videos that will go into more detail thank you for watching this video I hope you hope it helped you

30 comments

  1. I clicked on this hoping to see more of the ascending and descending tracts πŸ˜”. Nevertheless the content is dopeπŸ”₯πŸ”₯

  2. thank you..sir…
    but i request to you sir plz next vidio will make on spinal cord injury…πŸ‘
    your all vidios…are..amazing…thanx again ..😊

  3. The preparation for your videos must be unreal! Love the combination of art and science – truly educational and entertaining πŸ™‚

  4. Just a suggestion. I'd be more inclined to purchase your pictures if it was a package deal. ~$30 for all your pictures. Picking and choosing which ones I want adds up to soooo much that it's not really worth it imo unless you want maybe 1-5 specific lesson/pictures.

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